Desulfurization and conversion of hydrocarbonaceous black oils

ABSTRACT

A process for converting asphaltene-containing hydrocarbonaceous black oils into lower boiling, normally liquid hydrocarbon products. The process involves the integration of a thermal cracking coil and fixed-bed catalytic hydrogenation and desulfurization, and is especially applicable to sulfurous charge stocks containing less than 150 p.p.m. of metallic contaminants, and more than about 10.0 percent by volume of nondistillables. The charge stock is initially subjected to fixed-bed catalytic desulfurization and hydrogenation, and a series of separation steps to concentrate that portion of the reaction zone product boiling at temperatures above the normal gasoline boiling range. This high-boiling concentrate is then subjected to a noncatalytic, thermal cracking reaction zone or coil.

United States Patent [72] Inventors Frank Stolia Park Ridge; Laurence 0.Stine, Western Springs, both of ill. [211 App]. No. 771,250 [22] FiledOct. 28,1968 [45] Patented Nov. 2, 1971 [7 3] Assignee Universal OilProducts Company Des Plaines, Ill.

[54] DESULFURIZATION AND CONVERSION OF HYDROCARBONACEOUS BLACK OILS 8Claims, 1 Drawing Fig.

Make -up Hydrogen I: 4: 3

-3 Cold Separator Charge Healer Primary Examiner-Delbert E. GantzAssistant ExaminerBruskin Attorneys-James R. Hoatson, Jr. and Robert W.Erickson ABSTRACT: A process for convertingasphaltene-containinghydrocarbonaceous black oils into lower boiling, normally liquidhydrocarbon products. The process involves the integration of a thermalcracking coil and fixed-bed catalytic hydrogenation and desulfurization,and is especially applicable to sulfurous charge stocks containing lessthan 150 p.p.m. of metallic contaminants, and more than about 10.0percent by volume ofnondistillables. The charge stock is initiallysubjected to fixed-bed catalytic desulfurization and hydrogenation, anda series of separation steps to concentrate that portion of the reactionzone product boiling at temperatures above the normal gasoline boilingrange. This high-boiling concentrate is then subjected to anoncatalytic, thermal cracking reaction zone or coil.

Light Ends Recovery Cold Flash Ta Fracfianalian Flash FraclianatarVacuum Flash l6 Thermal 00/7 \25 Charge Slack Rasia'uum l APPLICABILITYOF INVENTION The process described herein is primarily adaptable to thedesulfurization of petroleum crude oil residuals having relatively lowmetals content i.e. containing less than l50 p.p.m. of total metals.More specifically, the present invention is directed toward acombination process for hydrogenating and desulfurizinghydrocarbonaceous charge stocks which are commonly referred to as blackoils. Petroleum crude oils, and particularly the heavy residualsextracted from tar sands, topped or reduced crudes, and vacuumresiduals, contain high molecular weight sulfurous compounds inexceedingly large quantities, nitrogenous compounds, asphaltic materialinsoluble in light hydrocarbons such as pentane and/or heptane, and highmolecular weight organometallic complexes. With respect to the metalliccomplexes, containing nickel and vanadium as the metallic components,the various black oil charge stocks can be classified as (1) highmetals" residuals, or (2) low metals" residuals. The present inventionis primarily directed to the processing of those hydrocarbonaceous blackoils having low metals content i.e. less than about 150 p.p.m. of totalmetals, computed as if existing in the elemental state. A black oilcharge stock is generally characteried as a heavy carbonaceous materialof which more than about 10.0 percent by volume boils above atemperature of l,050 F. (referred to as nondistillables). Such materialgenerally has a gravity less than about 20.0" API and sulfurconcentrations greater than about 2.0 percent by weight. With manystocks, the sulfur concentration can range as high as about 5.0 percentby weight. Conradson carbon residue factors generally exceed 1.0 percentby weight, and a great proportion of black oils indicate a Conradsonresidue factor above 10.0.

Exemplary of those black oils, to the conversion and desulfurization ofwhich the present invention is directed, include a crude tower bottomsproduct having a gravity of about 143 API and contaminated by thepresence of about 3.0 percent by weight of sulfur, 3,830 p.p.m. oftotalnitrogen, 85 ppm. of total metals, about 1 1.0 percent by weight ofinsoluble asphaltenes, and about 41.0 percent nondistillables. Thepresent invention affords the conversion of such charge stocks intolower boiling, normally liquid hydrocarbon products, and furtherconverts a considerable quantity of nondistillables. Additionally, thenormally liquid portion of the product effluent has been substantiallydesulfurized to a level less than about 1.0 percent by weight.

The principal difiiculty, heretofore barring the attainment of aneconomically feasible process, resides in the lack of sulfur stabilityof catalytic composites when the charge stock is characterized by thepresence of large quantities of asphaltic material and sulfur. Thisdifficulty arises primarily as a consequence of the necessity to effectthe process at operating s'everity levels such that nondistillableconversion simultaneously takes place while sulfurous compounds arebeing converted into hydrogen sulfide and hydrocarbons. Since theoperation must be effected at a high severity level, the asphalticmaterial, dispersed within of charge stock, has the tendency toflocculate and polymerize whereby the conversion thereof to morevaluable oil-soluble products is virtually precluded. Furthermore, thepolymerized asphaltic complexes become deposited upon the catalyticcomposite, steadily increasing the rate at which the same becomesdeactivated.

The present invention is founded upon recognition of the fact thatacceptable desulfurization of low metals-containing black oils ispossible at relatively mild operating severities which favor extendedcatalyst life without simultaneously effecting asphaltene polymerizationHydrogenation reactions are enhanced at lower severities, particularlywith respect to temperature. in order that the process becomeseconomically attractive from the standpoint of producing the lowerboiling, normally liquid hydrocarbon products, an essential feature ofthe present invention is the subsequent processing of the hydrogenatedand desulfurized product effluent from the fixed-bed catalytic reactionzone Therefore, as hereinafter set forth in greater detail, thedesulfurized catalytic reaction effluent is separated to produce ahydrocarbon stream boiling substantially completely above the gasolineboiling range, which hydrocarbon stream is subsequently subjected to anoncatalytic thermal reaction zone or coil.

OBJECTS AND EMBODIMENTS A principal object of our invention is toprovide an economical process for effecting the desulfurization andconversion of asphaltene-containing black oils to distillablehydrocarbons of lower molecular weight. A corollary objective is toextend the period of acceptable, economical catalyst life whiledesulfurizing and hydrogenating hydrocarbonaceous black oils containingless than about 150 p.p.m. of total metals.

Another object is to convert a sulfurous hydrocarbon charge stock, asignificant quantity of which exhibits a boiling range above atemperature of 1,050 E, into lower boiling distillable hydrocarbonshaving a sulfur concentration less than about 1.0 percent by weight.

In one embodiment, therefore, our invention relates to a process for theconversion of a sulfurous,.hydrocarbonaceous charge stock, of which atleast about 10.0 percent boils above a temperature of about l,050 F.,into lower boiling hydrocarbon products, which process comprises thesteps of: (a) heating said charge stock to a temperature of from 500 F.to about 775 F., reacting said charge stock with hydrogen in a firstreaction zone, in contact with the catalytic composite and at a pressureabove about l,000 p.s.i.g.; (b) separating the resulting reaction zoneeffluent, in a first separation zone, at substantially the same pressureimposed upon said first reaction zone, to provide a first vapor phaseand a first liquid phase; (c) separating said first vapor phase, in asecond separation zone, at substantially the same pressure imposed uponsaid first separation zone and at a reduced temperature to provide asecond vapor phase rich in hydrogen and a second liquid phase; (d)recycling at least a portion of said second vapor phase to said firstreaction zone; (e) separating at least a portion of said first liquidphase, in a third separation zone, at substantially the sametemperature, to provide a third vapor phase and a third liquid phase;(f) cracking at least a portion of said third liquid phase in anoncatalytic thermal cracking zone, (g) separating the resulting crackedproduct effluent in a fourth separation zone, at a reduced pressure offrom atmospheric to about p.s.i.g. to provide a fourth liquid phase anda fourth vapor phase; and, (h) further separating said fourth liquidphase, in a fifth separation zone, at a reduced pressure of fromsubatmospheric to about 50 p.s.i.g. to provide a fifth liquid phasecontaining distillable hydrocarbons, and an asphaltic residuum.

Other embodiments of our invention, as hereinafter set forth in greaterdetail, reside primarily in preferred ranges for process variables andin various processing techniques. For example, in another embodiment, atleast a portion of said fifth liquid phase is recycled to combine withsaid third liquid phase, to provide a combined feed ratio to saidthermal reaction zone of from about 1.121 to about 4.5:1. In aparticularly preferred embodiment, the fifth separation zone is a vacuumcolumn which serves to concentrate the unconverted asphaltic residuumand to provide at least a heavy vacuum gas oil, a light vacuum gas oiland a slop-wax cut. Generally, the latter, with or without a portion ofthe heavy vacuum gas oil, is recycled to the thermal cracking coil.Where the desired product distribution demands, a portion of theslop-wax cut may be recycled to combine with the fresh black oil chargeto the fixed-bed reaction zone. The total charge to the first, fixedbedcatalytic hydrogenation zone, including hydrogen recycle and makeuprequired to maintain pressure and supplant that which is consumed withinthe overall process, is heated to a temperature within the range of fromabout 650 to about 775 F. The precise temperature, to which the chargeto the catalytic reaction one is heated, is controlled within theaforesaid range by monitoring the temperature of the reaction zoneproduct effluent. Since the principal reactions being effectedareexothermic, a temperature rise is experienced as the charge and hydrogenpass through the catalyst bed. Economically acceptable catalyst life isachieved when the maximum'catalyst temperature, which is virtually thesame as that of the product effluent, is maintained at a maximum levelof about 800 F. In another embodiment, the first reaction zone emuent,being introduced into the first separation zone, is at a temperature offrom about 700 to about 775 F. in order that the heavier constituents ofthe reaction zone product eflluent are not carried over into theprincipally vaporous phase. Other objects and embodiments of ourinvention will be evident from the following, more detailed descriptionof the process encompassed thereby.

SUMMARY OF INVENTION As hereinbefore set forth, the principal functionof the present invention resides in the production of maximum quantitiesof distillable hydrocarbons which have been substantially reduced withrespect to sulfur concentration. Through the utilization of the presentcombination process, this is accomplished in a highly economical fashionwhile avoiding the difficulties of currently practiced processingtechniques. Paramount is the extension of the period of time duringwhich the fixed-bed of the solid catalytic composite functions in anacceptable manner. With respect to the processing of high metals" blackoils, being those containing more than about 150 ppm. of total metals,it has been found that a successful operation involves initiallyvisbreaking the fresh hydrocarbon charge stock in the presence oflimited quantities of hydrogen. Although both technical and economicaljustification exists to support this processing technique, there isincurred a yield loss with respect to that quantity of the originalnondistillable asphaltics which are not converted by way of catalyticprocessing. This yield loss results primarily from the fact that thermalcracking, in the presence of hydrogen, does not achieve the conversionof all the convertible asphaltics within the charge stock, theunconverted portion of which is removed from the system as an asphalticresiduum prior to subjecting the remainder of the thermally crackedproduct effluent to further conversion in the fixed-bed reaction zone.If the as-received high metals charge stock were processed initially inthe fixed-bed catalytic reaction zone, the presence of exceedingly highconcentrations of metals in an environment conductive to effectingacceptable desulfurization, results in extreme catalyst deactivation. inaccordance with the present process, primarily applicable to thosecharge stocks of low metals content, the residual charge stock iscatalytically desulfurized, and at least partially converted, atrelatively mild hydrogenation severities which favor extended catalystlife. The catalytically converted product effluent is subjected to aseries of separation steps in order to provide aliquid phasesubstantially free from gasoline boiling range hydrocarbons.

' This liquid phase is utilized as the charge to a noncatalytic thermalreaction zone, or coil. As hereinafter indicated, in a specific exampleintegrated into the description of the drawing, this particular processoffers maximum production of distillable hydrocarbons accompanied bymaximum desulfurization of the charge stock whose original metalscontent is less than about 150 p.p.m. In a preferred embodiment, thetotal charge to the fixed-bed catalytic reaction zone includes the freshhydrocarbon charge stock, a recycled hydrogen-rich gaseous phase, makeuphydrogen, and a recycled diluent, the source of the latter beinghereinafter set forth. This mixture is raised to a temperature offromabout 500 to about 775 F., as measured at the inlet to the catalyst bed.In order to preserve catalyst stability, the inlet temperature iscontrolled at a level such that the temperature of the reaction producteffluent, or

the maximum catalyst bed temperature, does not exceed about 800 F. Acertain measure of temperature control, within the fixed-bed ofcatalyst, is afforded through the conventional utilization of either aquench hydrogen stream, or quench liquid, or both, introduced at one ormore intermediate loci of the catalyst bed. The catalytic reaction zoneis maintained under an imposed pressure of from about l,000 to about4,000 p.s.i.g., and the hydrocarbon charge stock contacts the catalystat a liquid hourly space velocity of from about 0.5 to 10.0, based uponthe fresh hydrocarbon charge stock exclusive of recycled diluent and/orany quench streams employed for temperature control. The hydrogenconcentration will be in the range of from about 5,000 to about 50,000standard cubic feet per barrel, while the combined feed ratio, definedas total volumes of liquid charge per volume of fresh hydrocarboncharge, is in the range from about l.l:l to about 3.5 :l.

The catalytic composite disposed within the fixed-bed catalyticreaction, or conversion zone, can be characterized as containing ametallic component having hydrogenation activity, which component iscombined with a suitable refractory inorganic oxide carrier material ofeither synthetic, or natural origin. The precise composition and methodof manufacturing the carrier material is not considered essential to thepresent invention, although a siliceous carrier, such as 88.0 percent byweight of alumina and 12.0 percent by weight of silica, or 63.0 percentby weight of alumina and 37.0 percent by weight of silica are generallypreferred. Suitable metallic components having hydrogenation activityare those selected from the group consisting of the metals of GroupsVl-B and Vlll of the Periodic Table, as set forth in The Periodic Tableof The Elements, E. H. Sargent & Company, 1964. Thus, the catalyticcomposite may comprise one or more metallic components selected from thegroup of molybdenum, tungsten, chromium,

iron, cobalt, nickel, platinum, iridium, osmium, rhodium, ruthenium, andmixtures and compounds thereof. The concentration of the catalyticmetallic component, or components, is primarily dependent upon theparticular metal as well as the characteristics of the charge stock. Forexample, the metallic components of Group Vl-B are generally present inan amount within the range of from about l.0 percent to about 20.0percent by weight, the iron-group metals in an amount within the rangeof about 0.2 percent to about 10.0 percent by weight, whereas the noblemetals of Group Vlll are preferably present in an amount within therange of about 0.1 percent to about 5.0 percent by weight, all of whichare calculated as if these compounds existed within the catalyticcomposite in the elemental state. The refractory inorganic carriermaterial, with which the catalytic reactive metallic components arecombined, may comprise alumina, silica, zirconia, magnesia, Titaniaboria, strontia, hafnia, and mixtures of two or more includingsilica-alumina, alumina-silica-boron phosphate, silica-zirconiasilica-magnesia, silica-titania, alumina-zirconia, alumina-magnesia,silica-alumina-titania, alumina-magnesia-zirconia, silica-alumina-boria,etc. Before further summarizing our invention, several definitions arebelieved necessary in order that a clear understanding of the inventionbe afforded. in the present specification and the appended claims, thephrase pressure substantially the same as is intended to connote thepressure under which a succeeding vessel is maintained, allowing onlyfor the pressure drop experienced as a result of the flow of fluidsthrough the system. For example, where the catalytic first reaction zoneis maintained at a pressure of about 2,800 p.s.i.g., the firstseparation zone, or hot separator" will function at about 2,680 p.s.i.g.Similarly, unless otherwise specified, the phrase temperaturesubstantially the same as" is employed to indicate that the onlyreduction in temperature stems from normally experienced loss due to theflow of material from one piece of equipment to another, or from theconversion of sensible to latent heat by "flashing" where a pressuredrop occurs. When utilized, the term hydrocarbons boiling within thegasoline boiling range is intended to connote those normally liquidhydrocarbons boiling at temperatures up to about 400 or about 450 F.,including pentanes and heavier hydrocarbons, and, as in some localities,butanes. Likewise, a commonly referred to boiling range for gas oil isan initial boiling point of about 650 F. and an end boiling point ofabout l,050 F. The higher boiling 70.0 to about 80.0 percent thereof,the heavy gas oil, characteristically is considered having an initialboiling point of about 750 F. It is, of course, recognized that a lightgas oil" can have an initial boiling point as low as about 350 F. and anend boiling point as high as about 800 F. Similarly, the heavy gas oilcan have an initial boiling point as low as about 650 F.

The total product efi'luent from the catalytic reaction zone, at amaximum temperature of about 800 F., is passed into a first separationzone hereinafter referred to as the hot separator. The principalfunction served by the hot separator is to separate the mixed-phaseproduct effluent into a principally vaporous phase rich in hydrogen anda principally liquid phase containing some dissolved hydrogen. in apreferred embodiment, the total reaction product effluent is utilized asa heat-exchange medium in order to lower the temperature thereof to alevel in the range of from about 700 to about 775 F., and preferablybelow the level of 750 F. The principally vaporous phase from the hotseparator is introduced into a second separation zone hereinafterreferred to as the cold separator. The cold separator, operating atsubstantially the same pressure as the hot separator, but at asignificantly lower temperature in the range of about 60 to about 140 Fserves to concentrate the hydrogen in a second principally vaporousphase. The hydrogen-rich vapor phase, comprising about 82.5 mol percenthydrogen, and only about 2.3 mol percent propane and heavierhydrocarbons, is made available for use as a recycle stream to becombined with the fresh black oil charge stock. Butanes and heavierhydrocarbons are condensed in the cold separator, and removed therefromin a second principally liquid phase.

The first liquid phase from the hot separator may be in part recycled tocombine with the fresh hydrocarbon charge stock to serve as a diluentfor the heavier constituents thereof. The quantity of the liquid phasediverted in this manner is such that the combined feed ratio to thecatalytic reaction zone, being defined as total volumes of liquid chargeper volume of fresh liquid charge, is within the range of from about1.121 to about 3.5:l. The remaining portion of the principally liquidphase from the hot separator is introduced into a third separation onehereinafter referred to as the hot flash zone. The hot flash zonefunctions at about the same temperature as the liquid phase withdrawnfrom the hot separator, but at a significantly reduced pressure of fromabout 150 to about 350 p.s.i.g. The principally vaporous phase from thehot flash zone comprises primarily hydrocarbons boiling below atemperature of about 650 F and containing a relatively minor quantity ofhydrocarbons normally considered to be within the heavy gas oil boilingrange. This principally vaporous stream may be combined with the liquidstream from the cold separator, and the mixture introduced into a coldflash zone at a pressure of from atmospheric to about 60 p.s.i.g. and atemperature of from 60 to about 140 F.

The principally liquid phase withdrawn from the hot flash zone isintroduced into a thermal cracking reaction zone, or coil, atsubstantially the same temperature, and a pressure of from about 150 toabout 350 p.s.i.g. The thermally cracked product efi'luent, at atemperature of from about 875 to about 950 F., and a pressure of fromabout 40 to about 100 p.s.i.g., is cooled to a temperature of about 700F., and introduced into a fourth separation zone hereinafter referred toas the flash fractionator." The liquid phase from the flash fractionatoris introduced into a vacuum column maintained at about 25 to about 75mm. of Hg., absolute. The vacuum column serves as the fifth separationzone, the principal function of which is the concentration and separaterecovery of an asphaltic residuum, containing high molecular weightsulfurous compounds and being substantially free from distillablehydrocarbons. in general, gas oil streams are recovered from the vacuumcolumn as a separate light vacuum gas oil (LVGO) having a boiling rangeof from about 320 to about 750 F., a medium vacuum gas oil (MVGO)boiling from about 750 to about 980 F., and a heavy vacuum gas oilcontaining the remainder of the distillable hydrocarbons. it isunderstood that the particular boiling ranges of the various gas oilstreams, recovered from the vacuum column, are not essential to ourinvention, but will generally be determined by various refinery andmarketing demands. A preferred technique is to separate a slop-wax cut,from the vacuum column, which contains primarily these distillablesboiling above 980 F but may consist of up to about 30.0 percent byvolume of the total distillables boiling above 750 F. Although a portionof the slop-wax cut may be recycled to the catalytichydrogenation/desul-v furization reaction zone, it is generally recycledto the thermal coil in order to increase the yield of the more desirablegas oils. The amount of slop-wax so recycled is such that the combinedfeed ratio to the thermal reaction coil is above about 12:1 andgenerally not higher than about 3.0: l.

The principal advantages, or benefits, attendant the use of ourinvention, reside in 1 an extension of acceptable catalyst life withrespect to the fixed-bed catalytic reaction zone, which stems primarilyfrom the fact that desulfurization, to a level less than about 1.0percent by weight, is effected at a relatively low severity of operationwith the result that the atmosphere within the reaction one is notconductive to the formation of polymer products otherwise resulting fromthe presence of the hydrocarbon-insoluble asphaltenes; (2) a significantreduction in the required size of the vacuum flash column which, as willbe recognized by those having skill in the art of petroleum processingtechniques, affords an added advantage with respect to the overalleconomics of the process; and, (3) increased yields of the more valuablegas oils.

DESCRlPTION or DRAWING For the purpose of demonstrating the illustratedembodiment, and the utilization therein of the process of the presentinvention, the drawing will be described in connection with theconversion ofa vacuum column bottoms product having a gravity of 6.0 AP]and an ASTM 20.0 percent volumetric distillation temperature of aboutl,055 F. in addition, the charge stock contains 4,000 p.p.m. ofnitrogen, 5.5 percent by weight of sulfur, p.p.m. of nickel andvanadium, 6.0 percent by weight of heptane-insoluble asphaltenes and hasa Conradson carbon residue factor of 21.0 percent by weight. Thedescription will be directed toward a commercially scaled unit having acapacity of about 8,000 barrels per stream day. In the drawing, theembodiment is presented by means of a simplified flow diagram in whichsuch details as pumps, instrumentation and controls, heat-exchange andheatrecovery circuits, valving, startup lines and similar hardware havebeen omitted as nonessential to an understanding of the techniquesinvolved. The use of such miscellaneous appurtenances, to modify theillustrated process flow, are well within the purview of those skilledin the art. Similarly, it is further understood that the charge stock,stream compositions, operating conditions, design of fractionators,separators and the like are exemplary only, and may be varied widelywithout departure from the spirit of our invention, the scope of whichis defined by the appended claims.

It is intended that the charge stock be converted into maximumdistillable hydrocarbons which are recoverable by ordinary distillationtechniques in commonly utilized fractionation systems. The charge stockis processed in a fixed-bed catalytic desulfurization anddesulfurization zone in admixture with about 10,000 s.c.f./bl. ofhydrogen, based upon fresh feed exclusive of recycle streams, at acatalyst bed inlet temperature of about 700 F., and a pressure of about3,105 p.s.i.g. The liquid hourly space velocity, based upon fresh feedonly, is about 0.5, and the combined liquid feed ratio is about 2.0: l.

With respect now to the drawing, the charge stock, in an TABLE ll: HotSeparator Stream Analyses amount of about 7,678 bl./day (185.94mols/hr.), is introduced into the system by way of line 1, and followingheatexchange with various hot effluent streams, is passed into line 8 l12 heater in admixture with a recycled hydrogen-rich stream 5 from line3 and a hot separator bottoms liquid recycle in line Nitrogen l2.92 9.401.67 2. Makeup hydrogen, from a suitable external source, to mamHydrogen 76792 736' Isa-o taln plant pressure, and to replace thathydrogen consumed in Hydrogen Sulfide 90643 356}; the overall process,is introduced by way of line 4. The total charge to the heater is at atemperature of about 500 F.; this Mflhan, 88.95 mg, 2355 is increased toa level of about 700 F., as measured at the inlet Ethane 160.61 146.306.78 to the catalyst bed. The thus-heated total charge passes Pmpan 8952through line 6 into fixed-bed catalytic reaction one 7. The catalystdisposed in reaction one 7 is a composite of 88.0 per- 5 I if: 1'2: centby weight of alumina and 12.0 percent by weight of silica, Hem, 17:60 I5 with which is combined 2.0 percent by weight of nickel and about 16.0percent by weight of molybdenum, calculated as 3140 16,02 s theelemental metals. 320 520" F. 68.54 47.20 10.1 1

Component analyses of the total charge to reaction zone are 20-62650-750 F. so.s9 7.67 20.48 presented in table I. In the table, line 31ncludes both recycled and makeup hydrogen, line 2 1s the l1qu1d recyclefrom hot 750L980 F. I 129 La 60'" separator 9 and line 1 represents thetotal charge. PM 8. Residuum 149.72 70.94 TABLE I: Reaction one Charge25 It will be noted, from table II, that the material in line 10 is 3 21 75.5 mol percent hydrogen, and comprises only about 1.35

mol percent pentanes and heavier normally liquid hydrocar- Componentlbons. It is therefore, a principally vaporous phase. Likewise,

the stream in line 12 comprises about 19.9 mol percent bu- Nitrogen11.07 1.85 12.93 tanes and lighter material, exclusive of hydrogen whichis dis- "y l 843099 l75-52 8605-61 solved in the heavier hydrocarbons,and is considered, there- Hydrogen Sulfide 73902 26.36 765.38 fore a p py liquid p That portion of the hot separator bottoms stream not divertedthrough line 2, continues through line 12 into hot Ethane 133.14 7.53140.67 n h 13 A d r ff t d b r Propane use 7 7] as one re uc 1on 1npressure is e co e y means 0 a reducmg valve not indicated 1n thedrawmg, and the stream Bum" M49 L06 2655 40 enters hot flash one 13 at apressure of about 250 p.s.i.g. and a man 6.60 092 7.52 temperature ofabout 768 F. As herernafter set forth, the "cranes 4.70 1.29 5.99principal function of flash zone 13 is to concentrate the heaviercomponents in a liquid phase which serves as the charge to c,-' F. 2.003.19 5.19 thermal cracking coil 17. As seen in the following table lll,the Z- vaporous phase in line 14 comprises about 89.2 mol percent of228328, 5:: material boiling below about 520 F. exclusive of hydrogen,

' while the liquid stream in line 16 comprises about 6.3 mol per- HoaggyF. 67.16 67.16 cent exclusrve of hydrogen. 9x0 F.-Pl 9.27 9.27 Raiduum7M8 78.78 50 TABLE III: Hot Flash Zone Stream Analyses Charge Stock185.94

Line No. 14 16 The conversion product effluent, in mixed phase in line8, at 1 temperature of about 800 F., is utilized as a heat-exchangemedium, and is introduced into hot separator 9 at a temperature of 775'F. and a pressure of about 3,040 p.s.i.g. A prin- Nitrogen 1.45 0.12cipally vaporous phase is withdrawn by way of line 10, and a principallyliquid phase via line 12. In the present specifica- 6O Hydrogen 2H7tion, and in the appended claims, the terms "principally Mama 27 9 l Ivaporous" and principally liquid," are intended to describe a 1 Ema: 5particular stream, the major proportion of the components of Propane3.36 0.40 which are either normally gaseous, or normally liquid atstandard conditions. At least a portion of the liquid phase, 65 130mm1.61 014 withdrawn from hot separator 9, is diverted via line 2 to com-2'31" 3's: bine withthe fresh hydrocarbon charge stock, serving as adiluent for the heavier constituents thereof. The quantity of c 2 n b 76this recycled stream is 7,678 bl./day (460.15 mols/hr.), to pro- 5 .3 F.I vide a combined liquid feed ratio of 2.0: l. 520'-650 F. 4.7: 9.90 Theseparation of the reaction zone effluent, being effected 650'-750' F.3.10 17.37 in separator 9, is presented in the following table II,wherein line 8 is the feed to the separator (or the reaction zone ef-3233 -3f :3: fluent), l1ne 10 1s the vaporous phase and l1ne 12 1s thenet Relidu'um g liquid phase exclusive of the recycled portion in line2.

The liquid phase in line 16 is admixed with about 1.0 wt. percent of 230p.s.i.g. steam, and the mixture enters thermal coil 17 at a temperatureof about 740 F. and a pressure of about 170 p.s.i.g. The thermallycracked produce effluent, at a 7 pressure of about 55 p.s.i.g. and atemperature of about 930 F., and, after being cooled, passesvia line 18into a rectified flash fractionator 19 at a temperature of about 700 F.and a pressure of about 55 p.s.i.g. A vapor phase is withdrawn fromflash fractionator 19 through line 20, and a liquid phase through line24. The latter is introduced into vacuum flash column 25 at atemperature of about 750 F. The vacuum column is functioning at about 25mm. of Hg., absolute through the utilization of standard vacuum jetswhich are not illustrated in the drawing. The separation effected inflash fractionator 18 is presented in the following table 1V, along withthe component analysis of the thermally cracked product effluent in line18, exclusive of water.

The principally vaporous phase withdrawn from hot separator 9 throughline 10, is cooled to a temperature of about 120 F., and is introducedinto cold separator 11 at a pressure of about 3,000 p.s.1.g. Ahydrogen-rich gaseous phase is withdrawn through line 3, and is recycledtherethrough to combine with the fresh hydrocarbon charge stock inline 1. A principally liquid phase is withdrawn from cold separator l 1through line 15. The separation effected in cold separator 11, exclusiveof makeup hydrogen, is presented in the following table V.

TABLE V: Cold Separator Stream Analyses Line No. 3 15 Component.mole/hr.

Nitrogen 9.29 0.11 Hydrogen 7274.70 70.95 Hydrogen Sulfide 739.02 117.31

Methane 1091.19 37.29 Ethane 133.14 33.16 Propane 67.56 14.03

Butane: 24.49 10.44 Penranes 6.60 6.21 Hexane: 4.70 10.45

Vacuum flash column 25 serves to concentrate the residuum, 39.41mols/hr. leaving via line 28, and also to separate a light vacuum gasoil (LVGO), line 26 and a heavy vacuum gas oil (HVGO), line 27. TheHVGO, having a boiling range of 750 to 1,050 F., is in an amount ofabout 66.62 mols/hr., and the LVGO is in a amount of 58.45 mols/hr.Lighter material boiling below 320 F. is removed from vacuum flashcolumn 25 by the jets which are not indicated in the drawing.

Cold flash zone 21 has been illustrated for the sake of completeness,indicating the separation of the mixture of the hot flash vapors (line14), the flash fractionator vapors (line 20) and the cold separatorliquid (line 15). In a commercial installation, the vapors from theflash fractionator would be recovered separately due to the relativelyhigh degree of olefinicity thereof. Component analyses indicating theseparation effected in cold flash zone 21 are presented in the followingtable V1.

TABLE VI: Cold Flash Zone Stream Analyses Normally gaseous material isremoved via line 22 to a light ends recovery system, while nonnallyliquid hydrocarbons, including butanes, are removed via line 23 forfurther separation by fractionation The overall product yields,exclusive of normally gaseous material, but inclusive of butanes and thenormally liquid hydrocarbons recoverable from the vacuum jets and lightends recover (line 22), are presented in the following table V11.

750'-980 F. 60.6] 980' F.-Plus i0.0l Residuum 39.41

The sulfur concentration of the distillable hydrocarbon products isabout 0.83 percent by weight.

in a process in which the thermal coil is not an integral part, thefixed-bed catalytic reaction one must necessarily be operated at asignificantly higher severity level in order to produce the maximumquantity of distillables. The use of the present process affords areduction in operating severity, as measured by the catalyst bed inlettemperature, of from 50 to as much as 100 F. With respect to extendingthe period of time during which the catalytic composite functions in aneconomically acceptable manner, without experiencing deactivation, thepresent process increases catalyst life (expressed as barrels per pound)from 50 to'80 percent, resulting in longer on-stream cycles. A reductionin the size of the vacuum column, from a nominal diameter of 11.0 to 8.6feet, is made possible. This, as will be noted by those skilled in theart of petroleum processing techniques, affords a significant reductionin capital outlay for equipment.

The foregoing specification, and especially the example integratedwithin the description of the drawing, clearly illustrates the processof our invention and indicates the benefits afforded through theutilization thereof.

We claim as our invention:

1. A process for the conversion of a sulfurous, hydrocarbonaceous chargestock, of which at least about 10.0 percent boils above a temperature ofabout l,050 F., into desulfurized lower-boiling hydrocarbon products,which process comprises the steps of:

a. heating said charge stock to a temperature of from 500 to about 775F., reacting said charge stock with hydrogen in a catalytic reactionone, in contact with a catalytic composite and at a pressure above about1,000 p.s.i.g.

b. separating the resulting reaction zone effiuent, in a firstseparation one, at substantially the same pressure imposed upon saidfirst reaction one, and at a temperature of 700 to about 775 F., toprovide a first vapor phase and a first liquid phase;

cv separating said first vapor phase, in a second separation one, atsubstantially the same pressure imposed upon said first separation oneand at a reduced temperature, to provide a second vapor phase rich inhydrogen, and a second liquid phase;

d. recycling at least a portion of said second vapor phase to said firstreaction one;

e. separating at least a portion of said first liquid phase, in a thirdseparation zone at substantially the same temperature, and a reducedpressure of 150 to about 350 p.s.i.g. to provide a third vapor phase anda third liquid phase;

f. cracking at least a portion of said third liquid phase in anoncatalytic, thermal reaction zone g. separating the resulting crackedproduct effluent, in a fourth separation zone, at a reduced pressure ofform atmospheric to about p.s.i.g. to provide a fourth liquid phase anda fourth vapor phase; and,

h. further separating said fourth liquid phase, in a fifth separationzone, at a reduced pressure of from subatmospheric to about 50 p.s.i.g.toprovide an asphaltic residuum and a fifth liquid phase containingdistillable hydrocarbons of decreased sulfur content.

2. The process of claim 1 further characterized in that a portion ofsaid fifth liquid phase is recycled to combine with said third liquidphase, to provide a combined feed ratio to said thermal reaction one offrom about 1.2:1 to about 3.0: i.

3. The process of claim 1 further characterized in that said firstliquid phase is in part recycled to combine with said charge stock toprovide a combined feed ratio to said first reaction one of from aboutl.l:i to about 3.5: l

4. The process of claim 1 further characterized in that said chargestock is heated to a temperature in the range of from about 650 to about775 F.

5. The process of claim 1 further characterized in that said secondliquid phase and said third vapor phase are separated to recover anormally liquid hydrocarbon stream containing gasoline boiling rangehydrocarbons.

6. The process of claim 1 further characterized in that a portion ofsaid fifth liquid phase is recycled to combine with the charge stock tosaid catalytic reaction zone.

7. The process of claim 5 further characterized in that said secondliquid phase and said third vapor phase are combined and separated torecover a normally liquid hydrocarbon stream containing gasoline boilingrange hydrocarbons.

8. The process of claim 1 further characterized in that the portion ofsaid third liquid phase is introduced, without intermediate heatingthereof, into said thermal reaction zone.

2. The process of claim 1 further characterized in that a portion ofsaid fifth liquid phase is recycled to combine with said third liquidphase, to provide a combined feed ratio to said thermal reaction one offrom about 1.2:1 to about 3.0:1.
 3. The process of claim 1 furthercharacterized in that said first liquid phase is in part recycled tocombine with said charge stock to provide a combined feed ratio to saidfirst reaction one of from about 1.1:1 to about 3.5:1.
 4. The process ofclaim 1 further characterized in that said charge stock is heated to atemperature in the range of from about 650* to about 775* F.
 5. Theprocess of claim 1 further characterized in that said second liquidphase and said third vapor phase are separated to recover a normallyliquid hydrocarbon stream containing gasoline boiling rangehydrocarbons.
 6. The process of claim 1 further characterized in that aportion of said fifth liquid phase is recycled to combine with thecharge stock to said catalytic reaction zone.
 7. The process of claim 5further characterized in that said second liquid phase and said thirdvapor phase are combined and separated to recover a normally liquidhydrocarbon stream containing gasoline boiling range hydrocarbons. 8.The process of claim 1 further characterized in that the portion of saidthird liquid phase is introduced, without intermediate heating thereof,into said thermal reaction zone.